%I #5 Mar 31 2012 12:35:05
%S 1,28,82,242,716,2122,6296,18696,55554,165162,491240,1461628,4350278,
%T 12951392,38567446,114873170,342215676,1019662794,3038656824,
%U 9056682732,26996898534,80484319380,239970228042,715564197870
%N Number of base 28 n-digit numbers with adjacent digits differing by one or less.
%C [Empirical] a(base,n)=a(base-1,n)+3^(n-1) for base>=n; a(base,n)=a(base-1,n)+3^(n-1)-2 when base=n-1
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>1)+($[i+1]`-$[i]`>1))
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 26 2006
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